The overall objective of this long-term study has been to use an adoption design to disentangle genetic and rearing-family contributions to schizophrenia and related disorders. Beginning in 1969, a large Finnish national sample of adopting-away schizophrenic index mothers and matched control mothers, index and control adoptees, and index and control adoptive families was identified. In 1977, extensive interviewing and psychological testing were begun with the adoptees and the adoptive families by interviewers who were blind as to the biological parent status. Since 1982, the available biological parents have also been interviewed and tested. Working within a framework of a diathesis-stressor/protective factor model for the development of schizophrenic illness, the study has focused upon two major hypotheses: (1) the genetic liability to schizophrenia is significantly transmitted not only as narrowly defined schizophrenia but also in the form of other nonaffective psychoses and schizophrenia-related personality disorders; (2) genotype (indexed by psychiatric diagnosis and test measures of biological parents) and environment (indexed by measures of adoptive family relationships and communication) jointly predict additively and multiplicatively to the development of schizophrenia-related disorders in adopted-away offspring. Preliminary findings have strongly confirmed a genetic effect for nonaffective psychoses, less strongly for DSM-III-R schizophrenia; followup of adoptees will be necessary to clarify the hypothesized effect for schizophrenia-related personality disorders. Environmental influences have been implicated in that severe adoptee illness was found primarily in adoptees reared in families rated with severe relational disturbances, but not in index or control adoptees reared in "healthy" adoptive families. Genetic risk and independent clinical ratings of communication and affect in the adoptive parents jointly predicted to adoptee psychopathology. The main tasks planned for the renewal grant period are to complete the followup of adoptees at a median interval of 12 years after initial evaluation; to complete ratings and data reduction; and to conduct extensive data analyses, including attention to possible confounding variables, in order to evaluate the major hypotheses more definitively.